Metamerism is commonly seen in the members of phylum Annelida where the body is externally and internally divided into segments with a serial repetition of atleast some organs. Water canal system is present in the members of phylum Porifera. The body of ctenophores bears 8 external rows of ciliated comb plates which help in locomotion. Cnidoblasts or cnidocytes are characteristic feature of cnidarians (coelentrata).